The conserved amino-terminal domain of hSRP1α is essential for nuclear protein import

Karsten Weis, Ursula Ryder, Angus I. Lamond

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215 Citations (Scopus)

Abstract

Nuclear proteins are targeted through the nuclear pore complex (NPC) in an energy-dependent reaction. The import reaction is mediated by nuclear localization sequences (NLS) in the substrate which are recognized by heterodimeric cytoplasmic receptors. hSRP1α is an NLS-binding subunit of the human NLS receptor complex and is complexed in vivo with a second subunit of 97 kDa (p97). We show here that a short aminoterminal domain in hSRP1α is necessary and sufficient for its interaction with p97. This domain is conserved in other SRP1-like proteins and its fusion to a cytoplasmic reporter protein is sufficient to promote complete nuclear import, circumventing the usual requirement for an NLS receptor interaction. The same aminoterminal domain inhibits import of NLS-containing proteins when added to an in vitro nuclear transport assay. While full-length hSRP1α is able to leave the nucleus, the amino-terminal domain alone is not sufficient to promote exit. We conclude that hSRP1α functions as an adaptor to tether NLS-containing substrates to the protein import machinery.

Original languageEnglish
Pages (from-to)1818-1825
Number of pages8
JournalEMBO Journal
Volume15
Issue number8
Publication statusPublished - 15 Apr 1996

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Keywords

  • hSRP1α
  • NLS
  • Nuclear import
  • Nuclear localization signals
  • Protein transport

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